Our overall goal is to be able to understand the mechanisms by which hormones and growth factor-related proliferation and involution in mammary cancer in rats and mice and eventually to understand the mechanisms of human breast carcinogenesis and their prevention. Emphasis of the current project is the understanding of mammary carcinogenesis of mice and rats, integrating the use of cell and organismal biological approaches with those of molecular biology. Nandi will combine molecular biology approaches along with cell culture and in vivo studies to 1) conduct molecular analysis of known and novel oncogenes in MNU-induced precancerous and cancerous lesions originating in different mitogenic (hormones, growth factors, non-hormonal agents) environments; 2) determine the factors regulating the origin of hormone- dependent and -independent mammary tumors and 3) use endocrine manipulations to induce parity-like refractoriness to mammary carcinogenesis in virgin rats. Firestone's proposal focuses on the analysis of the molecular basis of the regulation of normal and tumor mammary cell growth and cell cycle control by TGFBeta. Initial studies will be done using newly developed immortalized normal, preneoplastic and neoplastic mammary epithelial cell lines of ductal or alveolar origin. To analyze he TGF-Beta effects on cell function, morphology, differentiation and receptor levels will be tested in ductal and alveolar-derived mammary cells. TGF-Beta induced and suppressed cell cycle-regulated genes will be identified by Northern analysis and functionally tested by their ability to disrupt the TGF-beta cell cycle arrest of transfection of "sense" and "anti-sense" expression vectors. Talamantes goal is to continue his analysis of the physiological factors involved in parity-induced refractoriness to mammary carcinogenesis in rats. Their findings have shown reduced growth hormone and prolactin levels and reduced estrogen receptors in the mammary gland of parous, compared with virgin rats. They have hypothesized that these hormones and receptors changes play a decisive role in making the parous rats refractory to mammary carcinogenesis. In the current studies, endocrine manipulations, radioimmunoassay, receptor analysis and transplantation studies will be undertaken to test their hypothesis. Cunha's approach is to examine the mechanisms of cell-cell interactions, which play a key role in the development, morphogenesis, growth and functional differentiation of the mouse mammary glands. He proposes to study the biology and mechanisms of action of mediators (Wnt-1 protein, Keratinocyte Growth Factor, TGF-alpha and retinoids) that are involved in or influence cell-cell interactions during early development of the mammary gland. His studies will use organ culture, developmental biological and molecular biological techniques.